This invention relates to an improved muffler system and more particularly pertains to an improved muffler system that can be mounted inside a restricted engine compartment such as the engine compartment of a small off-road vehicle.
In small off-road vehicles such as lawn tractors and riding mowers, it is important from both an aesthetic and a safety aspect that any muffler system associated therewith be mounted, as much as possible, inside the engine compartment.
Concerning safety, if the muffler system were externally mounted as shown in U.S. Pat. No. 3,796,277 to Gordon, it could accidentally be contacted by the vehicle operator or others thereby possibly causing them injury. In order to prevent injury from an externally mounted hot muffler as disclosed in U.S. Pat. No. 4,487,289 to Kicinski et al, it is known to provide a heat shield for insulating the muffler and to at least partially enclose both the muffler and heat shield inside the engine compartment.
However, by enclosing the muffler system inside the engine compartment proximate the engine, unacceptable heat radiation problems were initially encountered. For instance, if the muffler were located immediately adjacent a portion of the engine compartment shroud, heat radiating from the muffler system heated that portion of the shroud adjacent thereto to an unacceptable level such that another potential safety hazard was created thereby to the operator and others. Additionally, it was found that, due to the configuration of small vehicle engine compartments, heat radiated from the muffler system mounted in near proximity to the carburetor caused further problems by overheating the fuel in the carburetor causing fuel vapor lock.
Previous attempts to position a muffler system within the engine housing of a vehicle, such as a garden tractor, as disclosed in U.S. Pat. No. 4,265,332 to Presnall et al, were directed toward having the muffler surrounded by an open ended tubular heat shield having a venturi tube at its outer end which received and accelerated the exhaust gases to create a flow of cooling air through the engine housing and between the muffler and the tubular heat shield for extracting heat from both the engine housing and muffler. While the Presnall et al design did create a flow of cooler air through the engine housing, only one end of the muffler, the point where the air entered the space between the muffler and the heat shield, was relatively cooler while the remainder of the muffler system surface continued to radiate heat at an unacceptable level into the engine compartment.
Thus, there is a need for a muffler system which can be mounted in the limited space of a small off-road vehicle engine compartment which provides for the outer surfaces of the muffler system immediately proximate critical components within the engine compartment to be relatively cooler while the balance of the outer surfaces proximate non-critical components are allowed to become relatively hotter and which radiate the heat from the outer surface in controlled directions away from the critical components.